There are applications where there is a need for measuring the properties of a fluid in a tube of a shunt when the orientation and background pressure of the device cannot be accurately controlled, such as in the human body. Examples include the intracranial fluid (in the human brain) and the intraocular fluid (in the human eye). There are medically important features in both cases. For example, the flow rate for intracranial fluid is normally a slow 20 milliliters per hour, but its variation has clinical consequences. Shunts redirect this flow when the associated intracranial pressure becomes abnormally large and is characterized as the disease hydrocephalus. If the flow rate is partially interrupted, such as by an occlusion, the pressure can rise and the resulting rise in pressure can cause neurological damage.